1. Field of the Invention
This invention relates to a mechanical sealing device and, particularly to the technical field of a mechanical sealing device capable of effectively sealing high viscosity fluid or slurry-contained fluid.
2. Description of the Related Art
There has been a conventional mechanical seal as a related art of the invention, as shown in FIG. 5, which is a half sectional view of a conventional mechanical sealing device.
The mechanical seal 100 as the first related art shown in FIG. 5 is constituted as a set that is mounted on a rotary shaft 151 and installed within a stuffing box 150 through fastening bolts 160.
The mechanical seal 100 includes, as principle components thereof, a liquid sealing device 101, a fist seal flange 110, a second seal flange 120 and a gas sealing device that are arranged in order, from the inside of the stuffing box 150 toward the outside thereof, in the axial direction.
The liquid sealing device 101 is mounted on the outer circumference of a sleeve 153 secured onto the rotary shaft 151 through a screw socket 152. Between the rotary shaft 151 and the sleeve 153 fitting thereto is disposed an O-ring 154 for sealing therebetween.
In the liquid sealing device 101, a rotary seal ring 102 formed with a rotary seal face 103 is resiliently biased by a spring 105 through a U-shaped gasket 107 and a spacer 108.
Also, a stationary seal ring 112 having a stationary seal face 113 in contact with the rotary seal face 103 is fitted to the inner circumference of the first seal flange 110 through an O-ring 116. Further, at least one pin 115 secured to the stationary seal ring 112 engages a groove provided in the inner circumference of the first seal flange 110 to engage the stationary seal ring 112 with the first seal flange 110.
A gas-sealing device 121 is installed inside of the inner circumference of the second seal flange 120 coupled with the first seal flange 110. The gas-sealing device 121 is provided with a drive sleeve 125 that is secured to the sleeve 153 through at setscrew 126. A second rotary seal ring 122 having a second rotary seal face 123 is fitted in the drive sleeve 125 to slide therein. One end of a fluid passage formed in the second rotary seal ring 122 for creating dynamic pressure is opened at the second rotary seal face 123.
A second stationary seal ring 132 having a second stationary seal face 133 in close contact with the second rotary seal face 123 of the second rotary seal ring 122 is fitted to the inner circumference of the second seal flange 120 through an O-ring 136. In the second stationary seal face 133 are formed a plurality of grooves for creating dynamic pressure, in cooperation with the second rotary seal face 123. Also, the second rotary seal ring 122 is resiliently biased by a coil spring 127 toward the second stationary seal ring 132 side.
The mechanical seal 100 is assembled to the rotary shaft 151 and then the assembly is inserted and installed inside of inner circumferential surface 156 of the stuffing box 150.
An intermediate chamber 130 in which the gas-sealing device 121 is housed is constituted such that the pressure within the intermediate chamber 130 is approximately equal to the atmospheric pressure due to the presence of a drain 128 in the second seal flange 120.
On the other hand, there has been a tandem mechanical seal having a constitution approximately identical to that shown in FIG. 5 (not illustrated in the accompanying drawings. Because the corresponding components are different each other in geometry, each component identical to that in FIG. 5 shall be represented by a combination of the same numeral and a succedent alphabet.) However, the mechanical seal 100A as the second related art is different from the first related art in that the pressure within an intermediated chamber (buffering chamber) 130A is less than that within a liquid chamber 157 and more than the atmospheric pressure (the pressure within the intermediate chamber 130A is approximately a half of that within the liquid chamber 257.). The pressure within the intermediate chamber 130A can be derived from, for example, reducing the pressure within the liquid chamber 157.
It is also a difference from the first related art that a gas sealing device 121A is not a contact type sealing device employed in the first related art but is a non-contact type sealing device. Additionally, in a first seal flange 10A engaging a stationary seal ring, the inside diameter, on the intermediate chamber 130A side, of the first seal flange 110A is approximately equal to that of the stationary seal ring and it is adapted to prevent the pressure within the intermediate chamber 130A from acting on the side face of the stationary seal ring 112A.
If any high viscosity fluid or slurry contained fluid is intended to be sealed using such mechanical seals 100, 100A that are constituted as previously described, then slurries or the like that is contained in the fluid to be sealed will stick on the spacer 108, the spring 105, the gasket 107 and others. Then, those slurries and solid matters will enter between the sliding faces of those components to cause the axial response of the rotary seal ring to be reduced and the surface pressure of the rotary seal face 103 to be worsen, resulting in poor sealing ability.
Specifically, if the response of the rotary seal ring 102 is worsen in the state that the rotary seal face 103 of the rotary seal ring 102 is pushed against the stationary seal face 113, then the rotary seal face 103 will slides relative to the mating surface 113 in the state that the former is subject to a large pressure. Both seal faces will be therefore damaged due to heat generation from sliding action therebetween, causing the sealing ability to be worsen rapidly.
Contrary, if the response is worsen in the state that the surface pressure applied on the rotary seal face 103 is reduced, then the sealing ability of the mating seal faces will be reduced and slurries or the like enter between the rotary seal face 103 and the stationary seal face 113, which causes those seal faces to be damaged.
In such a structure of the mechanical seal 100 shown in FIG. 5, it is difficult to prevent the rotary seal face 103 from being damaged due to heat generation from sliding action, because it is difficult to cool the rotary seal face 103 and the proximity thereof by supplying coolant. This causes the sealing ability of the seal faces 103, 113 to be reduced.
Further, there exists, as the third related art of the invention, a mechanical seal 100B shown in FIG. 6, which has been used as a shaft sealing device in a stirrer, a pump and others for handling magnetic paint for a video tape. In other words, the fluid to be sealed contains slurry.
In FIG. 6, the mechanical seal is installed between a casing 201 and a rotary shaft 202.
As shown in FIG. 6, the rotary shaft 202 fits to and passes through a through-hole 201a. Between the rotary shaft 202 and the casing 201 is disposed a mechanical seal 100B that functions to divide off or tightly seal between a slurry contained fluid area 204 and a sealed liquid area 205.
The mechanical seal 100B is so constituted that a rotary seal ring 206 is fixedly fitted to the rotary shaft 202 and rotates therewith. An O-ring is disposed for sealing between the rotary shaft 202 and the rotary seal ring 206 in order to prevent fluid leakage. The rotary seal ring 206 has a rotary seal face, which in turn closely contacts a mating stationary seal face, thereby to function to seal.
On the other hand, a stationary seal ring 207 is slidably fitted in a through-hole 201A in the casing 201 through an O-ring 209. The O-ring 209 is inserted to fit in an annular groove 211 formed in the through-hole 201A of the casing 201 to seal the space 214 formed between the casing 201 and the stationary seal ring 207.
Also, the stationary seal ring 207 has a stationary seal face at its one end surface. The stationary seal face is in slide contact with the rotary seal face to prevent fluid from flowing into the sealed liquid area 205 from the slurry contained fluid area 204 even though in running condition. The stationary seal face is biased by a spring 210 to forcedly contact the rotary seal face.
During the running rotation of the rotary shaft 202, the sealed liquid 205B supplied to the sealed liquid area 205 through a sealed liquid feed passage 205A applies pressure on the rear of the stationary seal ring 207, thereby to secure that the rotary seal face and the stationary seal face can be in fully contact each other. Accordingly, the contact force between the stationary seal ring 207 and the O-ring 209 is kept to be small to allow the stationary seal ring 207 to displace in the axial direction.
In the mechanical seal 100B constituted as described, during the running of the rotary shaft 202, slurry contained fluid is forced to flow with high pressure and some deposit 204A of slurry contained fluid sinks to accumulate onto the space 214 close to the O-ring 209, and part of the deposit may enter the annular groove 211.
Thus, the response ability of the stationary seal ring 207 to displace axially to follow for the stationary seal face of the stationary seal ring 207 to closely contact the mating rotary seal face becomes poor, which prohibits the sealing action of the stationary seal face to exert. Furthermore, by the increase of accumulation of the deposit 204A in the space 214 and the annular groove 211 every repetition of running and stopping of the device, the stationary seal ring 207 decreasingly loses its ability to follow in the movement direction, resulting in leakage of the sealed fluid through the stationary seal face. This causes the mechanical seal 100B to be disassembled to clean.
Further, if the fluid to be sealed is fluidic foodstuff that is made into slurry by a foodstuff pump, slurries will stick onto the O-ring or the annular groove and then be mixed in during the next stirring process of foodstuff. This violates the Food Sanitation Law. To avoid such a problem, it is required to disassemble to clean the mechanical seal 100B before the start of operation at the next process.
In order to solve the problem described above, as shown FIG. 6, an injection passage 212 having an injection opening at a wall 201B of the casing 201 is provided. Cleaning fluid 212B pumped by a pump (not shown) passes through the injection passage 212. Further, a guide plate 215 is disposed at a position opposing the opening 212A of the injection passage 212 and functions to deflect the ejected cleaning fluid 212B toward the outer circumference of the stationary seal ring 207. After completion of the process operation, the cleaning fluid 212B is injected through the injection passage 212 to wash off the deposit 204A accumulated in the space 214 and the annular groove 211.
However, the injection of the cleaning fluid 212B through the injection passage 212 that is constituted as described above will help to stuff the deposit 204A present in the space 214 further inward of the annular groove 211. It is also a problem that the injection passage 212 is often clogged with the deposit 204A during operation. The clogging deposit 204A is disadvantageously mixed in the material at next process.
This invention is achieved in view of such problems as described previously, the technical problem to be solved by the invention is to prevent slurries, deposit and solid matter of the fluid from sticking onto the moving sections of a liquid sealing device to cause the movement of the moving sections to be worsen, resulting in poor sealing ability.
It is another technical problem to be solved by the invention is to improve and strengthen the sealing force, wherein a seal ring is biased with a resilient force of a packing mounted in the liquid sealing device and additionally with a fluid force acting on the packing.
It is further to maintain the surface pressure response to the seal face of the seal ring to be always constant.
It is also to cool fluid efficiently for preventing the increase of heat generation in sliding movement of the seal ring.
This invention is made to solve the technical problems above and therefore the technical means for solving them are constituted as follows.
The mechanical seal as the first embodiment according to the invention is one installed between a rotary shaft and a seal flange for sealing high viscosity fluid or slurry contained fluid, comprising: a first rotational seal ring having a relative face and retained with the rotary shaft; a first stationary seal ring having a seal face in close contact with the relative seal face and biased with a resilient means supported by the seal flange, the first rotational seal ring being engaged with the seal flange so as to rotate therewith; and an annular packing made of rubber-like elastic material, the annular packing having a secured section mounted with fluid tight to a retaining face on one side between the first stationary seal ring and the seal flange and having a seal lip section fitting with fluid tight to a contact face on the other side, the packing biasing the first stationary seal ring toward the seal face.
In the mechanical seal according to the first embodiment of the invention, the packing is, at its secured section, fixed with fluid tight on the retaining face of one member, while, at free end of its seal lip section, closely contact the mating face of the other member. Accordingly, when slurry contained fluid sticks, the packing elastically deforms at the seal lip section thereof, enabling the response to the surface pressure applied on the stationary seal ring to be always fully exerted.